Immune responses of elderly persons 4 years after receiving a live attenuated varicella vaccine

[Vaccines against Herpes zoster: Effectiveness, safety, and cost/benefit ratio]

CONTEXT

A vaccination against herpes zoster and its complication is available in France since June 2015. Its exact benefit for public health is still controversial and its level of protection is not optimal. All those reasons seem to suggest a low acceptation rate from general practitioners.

OBJECTIVE

To evaluate the effectiveness, the safety, and the cost/benefit ratio of the vaccination against herpes zoster in people aged 50 year or over.

DOCUMENTARY SOURCE

Systematic review in Medline and PubMed with research by key words: "herpes zoster vaccine", "zoster vaccine" and "post herpetic neuralgia vaccine".

SELECTION OF STUDIES

Randomized and observational studies published in English and French language have been selected by two readers.

RESULTS

On 1886 articles identified, 62 studies were included in this systematic review of which 21 randomized trials, 21 observational studies, and 17 medico-economic studies concerned the unadjuvanted vaccine. Considered studies showed an effectiveness of 50% against herpes zoster and 60% on post-herpetic neuralgia incidence of the unadjuvanted vaccine. Five randomized controlled studies were identified for the adjuvanted vaccine. The overall effectiveness of this vaccine was > 90% whatever the age of subjects including those over age 70 and 80. The medico-economic studies conducted in many countries have shown that vaccine policies were beneficial in individuals aged 60 years or over.

LIMITATION OF THE WORK

Most of data of effectiveness, and tolerance result from 2 large controlled studies only (SPS and ZEST) for the unadjuvanted vaccine and only one for the adjuvanted vaccine.

CONCLUSION

Despite controversy and few uncertainties, the vaccine significantly reduces herpes zoster and its complication incidence. In terms of public health objectives, it reduces the burden of the disease and has a positive medico-economic impact. Preliminary data concerning the adjuvanted vaccine, whilst very promising, are still too limited. Up to now, no group of people with particularly high risk of herpes zoster-related complication who will beneficiate the most of the vaccination has been identified yet and only an age criteria has been considered for the recommendation.

Broadly reactive human CD8 T cells that recognize an epitope conserved between VZV, HSV and EBV

Human herpesviruses are important causes of potentially severe chronic infections for which T cells are believed to be necessary for control. In order to examine the role of virus-specific CD8 T cells against Varicella Zoster Virus (VZV), we generated a comprehensive panel of potential epitopes predicted in silico and screened for T cell responses in healthy VZV seropositive donors. We identified a dominant HLA-A*0201-restricted epitope in the VZV ribonucleotide reductase subunit 2 and used a tetramer to analyze the phenotype and function of epitope-specific CD8 T cells. Interestingly, CD8 T cells responding to this VZV epitope also recognized homologous epitopes, not only in the other α-herpesviruses, HSV-1 and HSV-2, but also the γ-herpesvirus, EBV. Responses against these epitopes did not depend on previous infection with the originating virus, thus indicating the cross-reactive nature of this T cell population. Between individuals, the cells demonstrated marked phenotypic heterogeneity. This was associated with differences in functional capacity related to increased inhibitory receptor expression (including PD-1) along with decreased expression of co-stimulatory molecules that potentially reflected their stimulation history. Vaccination with the live attenuated Zostavax vaccine did not efficiently stimulate a proliferative response in this epitope-specific population. Thus, we identified a human CD8 T cell epitope that is conserved in four clinically important herpesviruses but that was poorly boosted by the current adult VZV vaccine. We discuss the concept of a “pan-herpesvirus” vaccine that this discovery raises and the hurdles that may need to be overcome in order to achieve this.

Human herpesviruses can cause a wide range of serious infections. They are extremely common and individuals remain latently infected lifelong, with reactivations often causing recurrent or severe disease. T-cells are important in controlling herpesvirus infections and preventing their reactivation, so vaccines that induce T-cells are likely to improve control. Here, we examined human T-cells against VZV that might allow focused vaccine development. We identified a dominant target against which the majority of subjects had mounted a CD8 T-cell response. We found that very similar targets also exist in three other important herpesviruses, HSV-1, HSV-2 and EBV. We showed that CD8 T-cells recognizing the VZV target could also recognize the others and we hypothesized that recurrent encounter with these viruses could boost this common response. In some individuals, immunization with a VZV vaccine did cause activation of these cells, but in most it did not. This reflects the variable efficacy of the currently available VZV vaccine. Our findings suggest that T-cell targets may be shared between herpesvirus species and may therefore contribute to a novel “pan-herpesvirus” vaccine. However, current VZV vaccines cannot reliably stimulate these T-cells and new strategies will be necessary to achieve this goal.

Prevention of shingles by varicella zoster virus vaccination

Herpes zoster is caused by reactivation from previous varicella zoster virus (VZV) infection, and affects millions of people worldwide. It primarily affects older adults and those with immune system dysfunction, most likely as a result of reduced or lost VZV-specific cell-mediated immunity. Complications include post-herpetic neuralgia, a potentially debilitating and chronic pain syndrome. Current treatment of herpes zoster and post-herpetic neuralgia involves antiviral agents and analgesics, and is associated with significant economic cost. Results from several clinical trials have determined that a live, attenuated VZV vaccine using the Oka/Merck strain (Zostavax) is safe, elevates VZV-specific cell-mediated immunity, and significantly reduces the incidence of herpes zoster and post-herpetic neuralgia in people over 60 years of age. Regulatory approval has recently been obtained and once launched, it is expected that this vaccine will significantly reduce the morbidity and financial costs associated with herpes zoster. Durability of vaccine response and possible booster vaccination will still need to be determined.

Herpes Zoster Risk Reduction through Exposure to Chickenpox Patients: A Systematic Multidisciplinary Review

Varicella-zoster virus (VZV) causes chickenpox and may subsequently reactivate to cause herpes zoster later in life. The exogenous boosting hypothesis states that re-exposure to circulating VZV can inhibit VZV reactivation and consequently also herpes zoster in VZV-immune individuals. Using this hypothesis, mathematical models predicted widespread chickenpox vaccination to increase herpes zoster incidence over more than 30 years. Some countries have postponed universal chickenpox vaccination, at least partially based on this prediction. After a systematic search and selection procedure, we analyzed different types of exogenous boosting studies. We graded 13 observational studies on herpes zoster incidence after widespread chickenpox vaccination, 4 longitudinal studies on VZV immunity after re-exposure, 9 epidemiological risk factor studies, 7 mathematical modeling studies as well as 7 other studies. We conclude that exogenous boosting exists, although not for all persons, nor in all situations. Its magnitude is yet to be determined adequately in any study field.

Immune senescence and vaccines to prevent herpes zoster in older persons

Varicella-zoster virus (VZV) T-cell-mediated immunity (VZV-CMI) in older persons prevents latent VZV in sensory neurons from reactivating to cause herpes zoster. VZV-CMI declines greatly with aging, but can be restored by the licensed zoster vaccine. However, the vaccine-induced boost in VZV-CMI (which determines the efficacy of the vaccine) is a function of the age of the vaccinee, and the duration of this boost wanes with time. Both factors influence the value of this vaccine. To understand these aging effects, limited information about the phenotypic and functional differences in VZV-CMI in old and young persons are reviewed, as well as the reversal of these differences by vaccination. Based on information from these studies some potential approaches to improving prevention of herpes zoster are discussed.

Simian varicella virus infection of Chinese rhesus macaques produces ganglionic infection in the absence of rash

Varicella-zoster virus (VZV) causes varicella (chickenpox), becomes latent in ganglia along the entire neuraxis, and may reactivate to cause herpes zoster (shingles). VZV may infect ganglia via retrograde axonal transport from infected skin or through hematogenous spread. Simian varicella virus (SVV) infection of rhesus macaques provides a useful model system to study the pathogenesis of human VZV infection. To dissect the virus and host immune factors during acute SVV infection, we analyzed four SVV-seronegative Chinese rhesus macaques infected intratracheally with cell-associated 5 × 10³ plaque-forming units (pfu) of SVV-expressing green fluorescent protein (n = 2) or 5 × 10⁴ pfu of wild-type SVV (n = 2). All monkeys developed viremia and SVV-specific adaptive B- and T-cell immune responses, but none developed skin rash. At necropsy 21 days postinfection, SVV DNA was found in ganglia along the entire neuraxis and in viscera, and SVV RNA was found in ganglia, but not in viscera. The amount of SVV inoculum was associated with the extent of viremia and the immune response to virus. Our findings demonstrate that acute SVV infection of Chinese rhesus macaques leads to ganglionic infection by the hematogenous route and the induction of a virus-specific adaptive memory response in the absence of skin rash.

VZV T cell-mediated immunity

Primary varicella-zoster virus (VZV) infection (varicella) induces VZV-specific antibody and VZV-specific T cell-mediated immunity. T cell-mediated immunity, which is detected within 1-2 weeks after appearance of rash, and consists of both CD4 and CD8 effector and memory T cells, is essential for recovery from varicella. Administration of a varicella vaccine also generates VZV-specific humoral and cellular immune responses. The memory cell responses that develop during varicella or after vaccination contribute to protection following re-exposure to VZV. These responses are subsequently boosted either by endogenous re-exposure (silent reactivation of latent virus) or exogenous re-exposure (environmental). VZV-specific T cell-mediated immunity is also necessary to maintain latent VZV in a subclinical state in sensory ganglia. When these responses decline, as occurs with aging or iatrogenic immune suppression, reactivation of VZV leads to herpes zoster. Similarly, the magnitude of these responses early after the onset of herpes zoster correlates with the extent of zoster-associated pain. These essential immune responses are boosted by the VZV vaccine developed to prevent herpes zoster.

National survey of primary care physicians regarding herpes zoster and the herpes zoster vaccine

BACKGROUND

This study describes physicians' perception of burden associated with herpes zoster (HZ) and postherpetic neuralgia (PHN), intentions for recommending the HZ vaccine, and perceived barriers to vaccination.

METHODS

A national survey of 438 general internal medicine (GIM) and 433 family medicine (FM) physicians was conducted during November-December 2005.

RESULTS

The survey response rate was 69%. Approximately 35% of GIM and FM physicians strongly agreed that HZ and PHN caused a significant burden of disease. For patients 60-79 years of age, > or =80% of GIM and FM physicians were somewhat or very likely to recommend HZ vaccine. In multivariate analyses, physicians who strongly agreed that HZ and PHN cause significant burden were more likely to recommend the vaccine to patients 60-79 years of age (odds ratio [OR], 2.75 [95% confidence interval [CI], 1.85-4.09]), whereas those who felt there was insufficient information about duration of protection (OR, 0.40 [CI, 0.24-0.67]), that the need to store HZ vaccine in a freezer was a definite barrier (OR, 0.31 [CI, 0.13-0.75]), or that their patients would not pay for the vaccine if it was not covered by insurance (OR, 0.57 [CI, 0.38-0.86]) were less likely to recommend it.

CONCLUSIONS

Primary care physicians perceived a high level of burden from HZ and PHN and generally favored the HZ vaccine.

Strategies for herpes zoster vaccination of immunocompromised patients

A vaccine to prevent herpes zoster (HZ) in adults > or =60 years of age with healthy immune systems was recently approved by the US Food and Drug Administration. This vaccine is contraindicated in persons with certain immunodeficiency states or who are receiving immunosuppressive therapy. On the basis of studies of the varicella vaccine in healthy and immunosuppressed children and studies of HZ vaccine in healthy adults before its licensure, a series of strategies are proposed for evaluating the live HZ vaccine in immunosuppressed persons. In addition, the use of other vaccines, including heat-inactivated or replication-defective varicella-zoster virus to prevent HZ in immunocompromised persons, is also discussed.

Immunization for the elderly

The morbidity and mortality of vaccine-preventable diseases among older adults are high. Despite the benefits of elderly vaccination, vaccination rates remain low and especially among some minority groups. Specific strategies for improving the rate of vaccination have been developed for medical offices and clinics, hospitals, and other health care institutions. There are vaccines that are recommended routinely for the elderly while other vaccines are recommended in certain circumstances. Knowing the indications, contraindications, and adverse reactions to the recommended vaccines for the elderly is very important to the primary care physicians.

Evaluation of the cost-effectiveness in the United States of a vaccine to prevent herpes zoster and postherpetic neuralgia in older adults

CONTEXT

A live-attenuated varicella-zoster virus vaccine, demonstrated to reduce the incidence of herpes zoster (HZ) and postherpetic neuralgia (PHN) and the morbidity associated with incident HZ and its sequelae, has recently been approved for use in the United States (U.S.).

OBJECTIVE

To examine the potential value of zoster vaccine for society and payers. DESIGN, SETTING AND POPULATION: An age-specific decision analytic model was designed to estimate the lifetime costs and outcomes associated with HZ, PHN and other HZ-related complications for vaccinated and non-vaccinated cohorts aged >or=60 years. Clinical trial data, published literature and other primary studies were used to inform the model. Robustness of results to key model parameters was explored through a series of one-way, multivariate and probabilistic sensitivity analyses. Both societal and payer perspectives were considered.

MAIN OUTCOME MEASURE

Incremental cost per quality-adjusted life year (QALY) gained.

RESULTS

For a representative cohort of 1,000,000 U.S. vaccine recipients aged >or=60 years, use of the zoster vaccine was projected to eliminate 75,548-88,928HZ cases and over 20,000 PHN cases. Over 300,000 outpatient visits, 375,000 prescriptions, 9,700 ER visits and 10,000 hospitalizations were projected to be eliminated with the vaccine translating into savings of US$ 82 million to US$ 103 million in healthcare costs associated with the diagnosis and treatment of HZ, PHN and other HZ-related complications. Cost-effectiveness ratios range from US$ 16,229 to US$ 27,609 per QALY gained, depending on the input data source and analytic perspective. Results were most sensitive to PHN costs, duration of vaccine efficacy, vaccine efficacy against PHN and HZ, QALY loss associated with pain states and complication costs.

CONCLUSIONS

The zoster vaccine at a price of US$ 150 is likely to be cost-effective for a cohort of immunocompetent U.S. vaccine recipients aged >or=60 years using commonly cited thresholds for judging cost-effectiveness. Conclusions are robust over plausible ranges of input parameter values and a broad range of scenarios and age cohorts.

Tolerability of treatments for postherpetic neuralgia

Herpes zoster occurs in up to 20% of people infected with varicella-zoster virus, due to reactivation of the virus from latently infected sensory ganglia. Although pain is a typical feature of acute zoster, pain persisting for more than a month after resolution of the rash is less common and is termed postherpetic neuralgia (PHN). The pain associated with PHN is neuropathic in origin and is notoriously difficult to treat. The incidence of herpes zoster and its associated complications both increase with age, so PHN should be seen more commonly in an aging population. Vaccination with live, attenuated varicella vaccine is safe and efficacious, particularly in children. It decreases the incidence of acute varicella and subsequent herpes zoster. Aciclovir is well tolerated, with renal toxicity only at high intravenous doses. Treatment of acute varicella with aciclovir attenuates acute illness but does not prevent herpes zoster. Treatment of herpes zoster with aciclovir or its derivatives minimises symptoms and may reduce the rate of PHN. Foscarnet is an alternative for an aciclovir-resistant virus but its use is limited by renal and CNS toxicity. Corticosteroids reduce acute pain in herpes zoster but do not affect the incidence of PHN. Their use in some patients may be limited by adverse effects such as gastritis and impaired glucose tolerance. Treatment of established PHN is difficult and may require a holistic approach. Tricyclic antidepressants and gabapentin are the systemic agents with the most proven benefit, although opioids such as oxycodone and NMDA receptor antagonists such as ketamine may be useful in some people. Adverse effects from tricyclic antidepressants are common but usually mild, while gabapentin is generally well tolerated. Although effective, the relatively common adverse effects of opioids and ketamine limit their usefulness in treating PHN. Topical treatment with 5% lidocaine patch or capsaicin is of benefit in some patients and is generally well tolerated. Intrathecal methyl prednisolone may be considered for intractable pain but efficacy and safety have not been confirmed.

Shingles Immunity and Health Functioning in the Elderly: Tai Chi Chih as a Behavioral Treatment

Both the incidence and severity of herpes zoster (HZ) or shingles increase markedly with increasing age in association with a decline in varicella zoster virus (VZV)-specific immunity. Considerable evidence shows that behavioral stressors, prevalent in older adults, correlate with impairments of cellular immunity. Moreover, the presence of depressive symptoms in older adults is associated with declines in VZV-responder cell frequency (VZV-RCF), an immunological marker of shingles risk. In this review, we discuss recent findings that administration of a relaxation response-based intervention, tai chi chih (TCC), results in improvements in health functioning and immunity to VZV in older adults as compared with a control group. TCC is a slow moving meditation consisting of 20 separate standardized movements which can be readily used in elderly and medically compromised individuals. TCC offers standardized training and practice schedules, lending an important advantage over prior relaxation response-based therapies. Focus on older adults at increased risk for HZ and assay of VZV-specific immunity have implications for understanding the impact of behavioral factors and a behavioral intervention on a clinically relevant end-point and on the response of the immune system to infectious pathogens.

A review of licensed viral vaccines, some of their safety concerns, and the advances in the development of investigational viral vaccines

Viral vaccines could be considered among the most important medical achievements of the 20th century. They have prevented much suffering and saved many lives. Although some curative antiviral drugs exist, we desperately depend on efforts by academic, governmental and industrial scientists in the advancement of viral vaccines in the prevention and control of infectious diseases. In the next decade, we hope to see advancement in the development of current and investigational viral vaccines against childhood and adult infections. In this article, we will review the licensed viral vaccines, some of their safety concerns, and the advances in the development of investigational viral vaccines.

Superiority of varicella skin test antigen over purified varicella-zoster virus glycoproteins in monitoring booster response to Oka varicella vaccine

Varicella skin test antigen has been developed based on the induction of delayed-type hypersensitivity (DTH) to varicella-zoster virus (VZV). The booster immune response to Oka varicella vaccine was assessed by cutaneous reactivity to purified VZV glycoprotein complexes, gB, gE:gI, gH:gL, and varicella skin test antigen. Skin tests with these antigens significantly augmented antibody production to glycoproteins and VZV antigen resulting in no further augmentation by the subsequent vaccination. All glycoprotein complexes induced the cutaneous reaction similarly to varicella skin test antigen. Cutaneous reaction to glycoproteins and varicella skin test antigen was boosted after vaccination. However, the magnitude of cutaneous reaction to each glycoprotein complex before and after vaccination was rich in variety. These results indicated that skin test with varicella skin test antigen is a more suitable indicator in monitoring cell-mediated immunity to VZV than that using purified glycoproteins.

Vaccines and immunotherapies for the prevention of infectious diseases having cutaneous manifestations

Although the development of antimicrobial drugs has advanced rapidly in the past several years, such agents act against only certain groups of microbes and are associated with increasing rates of resistance. These limitations of treatment force physicians to continue to rely on prevention, which is more effective and cost-effective than therapy. From the use of the smallpox vaccine by Jenner in the 1700s to the current concerns about biologic warfare, the technology for vaccine development has seen numerous advances. The currently available vaccines for viral illnesses include Dryvax for smallpox; the combination measles, mumps, and rubella vaccine; inactivated vaccine for hepatitis A; plasma-derived vaccine for hepatitis B; and the live attenuated Oka strain vaccine for varicella zoster. Vaccines available against bacterial illnesses include those for anthrax, Haemophilus influenzae, and Neisseria meningitidis. Currently in development for both prophylactic and therapeutic purposes are vaccines for HIV, herpes simplex virus, and human papillomavirus. Other vaccines being investigated for prevention are those for cytomegalovirus, respiratory syncytial virus, parainfluenza virus, hepatitis C, and dengue fever, among many others. Fungal and protozoan diseases are also subjects of vaccine research. Among immunoglobulins approved for prophylactic and therapeutic use are those against cytomegalovirus, hepatitis A and B, measles, rabies, and tetanus. With this progress, it is hoped that effective vaccines soon will be developed for many more infectious diseases with cutaneous manifestations.

Cost containment analysis of childhood vaccination against varicella in Israel

OBJECTIVES

The low cost of safe and effective vaccines prompted a cost-containment evaluation of a nationwide vaccination campaign against varicella.

METHODS

A model incorporating demographic, epidemiologic and economic data from Israeli sources (supplemented by data from International literature) was constructed to estimate the decrease in morbidity and the consequent reductions in treatment costs and time-off work of a nationwide programme vaccinating children at 12 months.

RESULTS

A policy of aiming to immunize a cohort of all 1-year-olds in Israel in the year 2002, for an annual cost of $1.10 million to the health services and $1.27 million to society (including lost work and transport costs), would reduce the number of cases of varicella during the lifetime of a cohort from 123,984 to 10,170 cases. This morbidity reduction would reduce national expenditures by $1.80 million in health service resources alone and by $24.5 million to society, mainly due to inaverted work absences. In addition an estimated 0.93 lives, representing 38.6 life years will be saved in the cohort.

CONCLUSIONS

Under an assumption of neutrality relating to the potential effects of vaccination on herpes zoster virus, our model based calculations show that a national varicella vaccination programme is likely to be cost saving, not only from a societal perspective but also from the narrower health service perspective.

Effects of a behavioral intervention, Tai Chi Chih, on varicella-zoster virus specific immunity and health functioning in older adults

OBJECTIVE

Both the incidence and severity of herpes zoster (shingles) increase markedly with increasing age in association with a decline in varicella-zoster virus (VZV) specific cell-mediated immunity (CMI). This study examined whether a behavioral intervention, Tai Chi Chih (TCC), affects VZV specific immunity and health functioning in older adults who, on average, show impairments of health status and are at risk for shingles.

METHODS

Thirty-six men and women (age > or =60 years) were assigned randomly to a 15-week program of TCC instruction (three 45 minute classes per week; N = 18) or a wait list control condition (N = 18). VZV-specific CMI was measured at baseline and at 1-week postintervention. Health functioning (Medical Outcome scale: SF-36) was assessed at baseline, and at 5, 10, and 15 weeks during the intervention, and at 1-week postintervention.

RESULTS

In the intent-to-treat sample, VZV-specific CMI increased 50% from baseline to 1-week postintervention in the TCC group (p < 0.05) but was unchanged in the wait list control group. In those who completed the study, 1-week postintervention SF-36 scale scores for role-physical (p < 0.05) and physical functioning (p < 0.05) were higher in the TCC group (N = 14) as compared with controls (N = 17). Older adults who had impairments of physical status at baseline showed the greatest increases of SF-36 role-physical (p < 0.01) and physical functioning (p < 0.001) during the TCC intervention.

CONCLUSIONS

Administration of TCC for 15 weeks led to an increase in VZV-specific CMI. Gains in health functioning were found in participants who received TCC and were most marked in those older adults who had the greatest impairments of health status.

The incidence of shingles and its implications for vaccination policy

A vaccine is now available to prevent varicella-zoster infection, but its place in routine preventive care is not yet determined. The age specific incidence of shingles was examined separately by gender and age groups (15-24, 25-44, 45-64, 65-74 and 75 years and more) over the years 1994-2001. These incidence data were applied to national available data for the UK on current life expectancy to calculate the risk of shingles infections at varying ages. The potential benefit of an effective vaccine was estimated using three models of vaccine efficacy applied separately to males and females at ages 50, 60 and 65 years and assuming vaccination at a single age. Similar calculations were made using a two dose strategy at age 45 and 65 years and at age 50 and 70 years. The cost per case saved was estimated from a vaccination cost of pound 40 per dose. The probability of having had an attack of shingles before age 45 years is 8.6% for males and 10.5% for females, The risk of acquiring shingles over an expected lifetime (assuming no preventive vaccination) for males aged 45 years is 22% and for females 32%. Whichever vaccine efficacy model was chosen, a single vaccination policy at age 65 years was the most favourable option in both males and females. A two age vaccination policy was estimated to increase the cost per case saved by 30% over a single age policy but administration at age 50 and 70 years substantially increased the number of cases saved as compared with a single age policy and was potentially better than vaccination at 45 and 65 years.

Induction of humoral and cell-mediated immunity to hepatitis B surface antigen by a novel adjuvant activity of Oka varicella vaccine

Oka varicella vaccine induces humoral and cell-mediated immunity to varicella-zoster virus (VZV), even in immunocompromised hosts. This vaccine showed novel adjuvant activity against co-inoculated hepatitis B surface antigen (HBsAg). Either a mixed inoculation of HBsAg with heat-inactivated Oka varicella vaccine at one site or a separate inoculation of HBsAg and live vaccine at different sites induced an antibody response but failed to induce delayed type hypersensitivity (DTH) to HBsAg. In contrast, immunization of HBsAg mixed with live vaccine induced DTH and an enhanced antibody response to HBsAg. The adjuvant activity of Oka varicella vaccine was similar in terms of antibody production to that of alum adjuvant. A T helper cell-dominant immunity to VZV and HBsAg continued for 1 year. Oka varicella vaccine combined with a foreign antigen may serve as a novel polyvalent vaccine for the infectious diseases for which cell-mediated immunity is beneficial.

Prophylaxis of herpesvirus infections in immunocompetent and immunocompromised older patients

In older patients, prophylaxis of herpesvirus infections mainly involves preventing the recurrence of herpes simplex virus (HSV) and complications of herpes zoster in immunocompetent patients, while in immunocompromised patients it is more concerned with the prevention of opportunistic virus reactivation. HSV ocular infection is the most frequent cause of corneal blindness in the US. The effectiveness of aciclovir 400mg twice daily in preventing the recurrence of HSV eye disease in immunocompetent patients has been well demonstrated. The issue of treatment duration for patients with highly recurrent ocular herpes remains unresolved. Post-herpetic neuralgia (PHN) is one of the most common neuralgic illnesses worldwide. Some progress in prevention of PHN has been made with a combination of antiviral therapy (famciclovir or valaciclovir), started within 72 hours of onset of the rash, and analgesic treatment. However, the best prevention of PHN is the prevention of herpes zoster disease, and the varicella vaccine is an option which over the next few years will be tested in clinical trials. For immunocompromised patients of any age, restoring immunity prevents herpesvirus disease, as demonstrated for cytomegalovirus (CMV) in AIDS patients receiving highly active antiretroviral therapy. Specific antiviral therapy during the initial period after transplantation could prevent reactivation of HSV or CMV in seropositive recipients. Whether pre-emptive therapy or prophylaxis with ganciclovir is the optimal approach against CMV remains controversial, and the relative merits and limitations of each approach may guide the choice. In stem cell transplantation, pre-emptive therapy with foscarnet avoids the neutropenia and related complications associated with ganciclovir. In renal transplant recipients, universal prophylaxis of CMV infection with valaciclovir has the same efficacy as ganciclovir. Although it is relatively toxic, cidofovir should be further evaluated because of its in vitro activity against most DNA viruses.

Vaccination to prevent varicella and shingles

Vaccination of healthy children against varicella using the live attenuated Oka vaccine has been available in Japan and south Korea for several years. In 1996, a programme of universal vaccination of children to prevent varicella was introduced in the USA and other countries, including Canada, Germany, and Sweden, have licensed the vaccine for use in healthy children. This article reviews the origin of the Oka vaccine and the evidence for vaccine safety and efficacy in children and adults. Universal vaccination of children and targeted vaccination of groups at risk of severe varicella are discussed. The possible use of the Oka vaccine to prevent zoster is reviewed, and initiatives to develop new varicella zoster virus vaccines are outlined.

The current status of live attenuated varicella vaccine

This manuscript reviews the means by which live attenuated varicella vaccine offers protection against varicella and zoster. It is accepted that although varicella is usually a mild illness, complications leading to morbidity and mortality are significant and the disease is worth preventing. The vaccine offers close to 100% protection from severe chickenpox and 90% protection from illness. Waning of immunity after vaccination, particularly in children, has not been a significant problem. Ways in which vaccination may decrease the incidence and severity of zoster include the following. Vaccine virus may be less likely to establish latency and to be able to reactivate than wild type virus. In addition, by selective immunization of certain hosts such as HIV-infected children whose, immune systems are still relatively intact and individuals with latency due to wild type virus to boost the cell-mediated immune response to the virus, zoster may be decreased. Varicella vaccine is predicted to have a major impact on the epidemiology of varicella and zoster in countries with high vaccine uptake.

Live-attenuated varicella vaccine

This article reviews the history and development of live attenuated varicella vaccine from its early days in Japan to its widespread use throughout the world. The vaccine has proven extremely safe after immunization of as many as 10 million healthy children and adults in the United States alone. The vaccine is also highly immunogenic and offers close to 100% protection from severe chickenpox and 90% protection from illness. It is expected to have a major impact on the epidemiology of varicella and zoster in countries with high vaccine uptake.

Vaccines in the 21st century

Steffens was wrong about the Soviet Union, and I may well be wrong about the future of vaccines; however, in Table 13, I give my [table: see text] prediction of the vaccination schedule of the next century. It is an optimistic vision, so let us hope that I am right.

Travel-related vaccines

Travelers are at increased risk for several infections, including familiar infections such as measles that are widely distributed but more common in developing countries. Vaccines can markedly decrease the risk for many of these infections and are an important part of pretravel preparation. Travel provides an opportunity to review and update routine vaccines in adults and assess risk from unusual infections. Global travel is growing. Persons who are elderly, HIV-infected, and immunocompromised account for many of the travelers. Studies that assess the immunogenicity, efficacy, and adverse effects of some of the special vaccines used primarily in travelers generally have been done in young, healthy populations. Findings in young adults do not apply to other populations in whom immune response can be slower, less effective, and less durable. Recent reports of severe adverse events in elderly persons who have received yellow fever vaccine are a reminder that widely used, old vaccines can have unexpected side effects when used in a new population. It is biologically plausible that adverse effects might be more common in the elderly, and epidemiologically plausible that occasional instances of similar adverse events in the past could have been missed. Studies on special and travel vaccines in the elderly are needed urgently to define how these vaccines should be used in older populations and whether alternative means for protection are needed.

Comparison of a live attenuated and an inactivated varicella vaccine to boost the varicella-specific immune response in seropositive people 55 years of age and older

Healthy, varicella-zoster virus (VZV)-seropositive subjects, aged 55-89 years (mean age 66 years), received either 4000 PFU of live, attenuated VZV vaccine (n=85) or an equal volume of this vaccine that was heat-inactivated (n=82). Both vaccines significantly boosted VZV antibody (enzyme immunoassay) and gamma-interferon production by peripheral blood mononuclear cells stimulated by VZV antigen. These responses returned to baseline by 12 months. Circulating mononuclear cells that proliferated in response to VZV antigen were significantly more numerous (responder cell frequency assay) after either vaccine, and persisted with a half-life of 17. 5-21.3 months. There were no differences in immune response to either vaccine in this older age cohort.

Immunology of Varicella Immunization in the elderly

OBJECTIVE

To review the varicella-zoster virus (VZV) and herpes zoster disease and to summarize published reports on the use of the live-attenuated varicella zoster vaccine to enhance cell-mediated immunity in elderly individuals.

DATA SOURCE

A MEDLINE search (1966-August 1999) for English-language clinical studies and review articles pertaining to VZV and the live-attenuated varicella vaccine was conducted; references obtained from these publications were subsequently reviewed for additional relevant articles.

STUDY SELECTION AND DATA EXTRACTION

Representative clinical trials were summarized and relevant information was selected to assist in the understanding of VZV, the subsequent immune response, and the live-attenuated varicella vaccine.

DATA SYNTHESIS

The physiologic, age-related decline in VZV cell-mediated immunity has been shown to be restored on administration of live-attenuated varicella vaccine. Various studies report serum anti-VZV antibody concentrations, and production of interferon-gamma were increased following vaccination. Concentrations subsequently returned to baseline one year after vaccination. Increase in responder cell frequency, a measure of cell-mediated immunity, has been reported to last up to four years after vaccination, at concentrations similar or superior to those observed following herpes zoster.

CONCLUSIONS

Enhancement of cell-mediated immune response in elderly individuals through vaccination with live-attenuated varicella vaccine is a possible measure to protect this population from herpes zoster and to attenuate its complications. A summary of immunogenicity studies to identify the immune response to live-attenuated varicella vaccine in the elderly is presented. The absolute clinical significance, as well as appropriate administration guidelines of this prophylactic intervention, will become evident following forthcoming large, masked, placebo-controlled trials.

Varicella zoster virus

Because of its ability to produce two clinically distinct disease entities (chickenpox and shingles), varicella zoster virus (VZV) is an unusual etiologic agent. Although in the past viral exanthems were mostly only of academic interest to the practitioner, the development of antiviral agents and the newly approved varicella (OKA) vaccine have increased the clinical significance. Also, with the increasing seroprevalence of HIV infection, more patients will be stricken with zoster (at a younger age) and disseminated varicella. In this review, the history, incidence, pathogenesis, clinical manifestations, and treatment options (of VZV infection and postherpetic neuralgia) will be discussed.

Current pharmacological approaches to the therapy of varicella zoster virus infections: a guide to treatment

Varicella zoster virus (VZV), a member of the herpesvirus family, is responsible for both primary (varicella, chickenpox) as well as reactivation (zoster, shingles) infections. In immunocompetent patients, the course of varicella is generally benign. For varicella zoster, post-herpetic neuralgia is the most common complication. In immunocompromised patients (particularly those with AIDS), transplant recipients and cancer patients, VZV infections can be life-threatening. For these patients and also for immunocompetent patients at risk such as pregnant women or premature infants, the current treatment of choice is based on either intravenous or oral aciclovir (acyclovir). The low oral bioavailability of aciclovir, as well as the emergence of drug-resistant virus strains, have stimulated efforts towards the development of new compounds for the treatment of individuals with VZV infections. Among these new compounds, penciclovir, its oral prodrug form famciclovir and the oral pro-drug form of aciclovir (valaciclovir), rank among the most promising. As with aciclovir itself, all of these drugs are dependent on the virus-encoded thymidine kinase (TK) for their intracellular activation (phosphorylation), and, upon conversion to their triphosphate form, they act as inhibitors/alternative substrate of the viral DNA polymerase. Therefore, cross-resistance to these drugs may be expected for those virus mutants that are TK-deficient and thus resistant to aciclovir. Other classes of nucleoside analogues dependent for their phosphorylation on the viral TK that have been pursued for the treatment of VZV infections include sorivudine, brivudine, fialuridine, fiacitabine and netivudine. Among oxetanocins, which are partially dependent on viral TK, lobucavir is now under clinical evaluation. Foscarnet, which does not require any previous metabolism to interact with the viral DNA polymerase, is used in the clinic when TK-deficient VZV mutants emerge during aciclovir treatment. TK-deficient mutants are also sensitive to the acyclic nucleoside phosphonates (i.e. [s]-1-[3-hydroxy-2-phosphonylmethoxypropyl]cytosine; HPMPC); these agents do not depend on the virus-encoded TK for their phosphorylation but depend on cellular enzymes for conversion to their diphosphoryl derivatives which then inhibit viral DNA synthesis. Vaccination for VZV has now come of age. It is recommended for healthy children, patients with leukaemia, and patients receiving immunosuppressive therapy or those with chronic diseases. The protection induced by the vaccine seems, to some extent, to include zoster and associated neuralgia. Passive immuniatin based on specific immunoglobulins does not effectively prevent VZV infection and is therefore restricted to high risk individuals (i.e. immunocompromised children and pregnant women).

Effect of shipment, storage, anticoagulant, and cell separation on lymphocyte proliferation assays for human immunodeficiency virus-infected patients

Lymphocyte proliferation assays (LPA), which can provide important information regarding the immune reconstitution of human immunodeficiency virus (HIV)-infected patients on highly active antiretroviral therapy, frequently involve shipment of specimens to central laboratories. In this study, we examine the effect of stimulant, anticoagulant, cell separation, storage, and transportation on LPA results. LPA responses of whole blood and separated peripheral blood mononuclear cells (PBMC) to different stimulants (cytomegalovirus, varicella-zoster virus, candida and tetanus toxoid antigens, and phytohemagglutinin) were measured using fresh specimens shipped overnight and frozen specimens collected in heparin, acid citrate dextrose (ACD), and citrate cell preparation tubes (CPT) from 12 HIV-infected patients and uninfected controls. Odds ratios for positive LPA responses were significantly higher in separated PBMC than in whole blood from ACD- and heparin-anticoagulated samples obtained from HIV-infected patients and from ACD-anticoagulated samples from uninfected controls. On separated PBMC, positive responses were significantly more frequent in fresh samples compared with overnight transportation for all antigens and compared with cryopreservation for the candida and tetanus antigens. In addition, viral antigen LPA responses were better preserved in frozen PBMC compared with specimens shipped overnight. CPT tubes yielded significantly more positive LPA results for all antigens, irrespective of the HIV patient status compared with ACD, but only for the candida and tetanus antigens and only in HIV-negative controls compared with heparin. Although HIV-infected patients had a significantly lower number of positive antigen-driven LPA responses compared with uninfected controls, most of the specimen processing variables had similar effects on HIV-positive and -negative samples. We conclude that LPA should be performed on site, whenever feasible, by using separated PBMC from fresh blood samples collected in either heparin or ACD. However, if on-site testing is not available, optimal transportation conditions should be established for specific antigens.

Live attenuated varicella vaccine

Varicella-zoster virus (VZV) is a ubiquitous human pathogen that causes varicella, commonly called chicken pox; establishes latency; and reactivates as herpes zoster, referred to as shingles. A live attenuated varicella vaccine, derived from the Oka strain of VZV has clinical efficacy for the prevention of varicella. The vaccine induces persistent immunity to VZV in healthy children and adults. Immunization against VZV also has the potential to lower the risk of reactivation of latent virus. The varicella vaccine may eventually reduce or eliminate herpes zoster, which is a serious problem for elderly and immunocompromised individuals.

Pain and its persistence in herpes zoster

The nature and duration of pain associated with herpes zoster is highly variable. This review of research on pain in acute herpes zoster and postherpetic neuralgia (PHN) explores those observations relevant to the definition and pathogenesis of PHN and the design of treatment trials. A model for the pathogenesis of PHN is presented, which gains support from studies of risk factors. Several directions for future research are identified.

Assays for antibodies to varicella-zoster virus

Anti-varicella-zoster virus serum antibody assays and their use in vaccine development are described. Of particular interest are FAMA and neutralization assays and the gpELISA. These and other assays are compared and summarized in terms of characteristics including biologic relevance, sensitivity, specificity, and suitability for different laboratory and clinical applications.

The varicella vaccine. Clinical trials in immunocompromised individuals

A review of the use of live attenuated varicella vaccine in immunocompromised children, particularly those with underlying leukemia in remission, is presented. Data concerning safety, immunogenicity, and efficacy of this vaccine in high-risk children are reviewed. The unique contributions toward our understanding of varicella vaccine, including spread of vaccine-type virus, incidence of zoster, and immune correlates provided by studies of immunocompromised patients are discussed. The importance of protecting high-risk children against severe varicella by the use of varicella vaccine is apparent.

Immune responses to varicella-zoster virus

The host response to VZV is critical to the outcome of primary VZV infection. The maintenance of immune memory to the virus is required to prevent symptomatic re-infection on exogenous re-exposure to VZV and to prevent symptomatic reactivation of endogenous virus. Immunization with live varicella (Oka) vaccine elicits primary and memory immunity to VZV. Humoral and cell-mediated host responses induced by the wild-type virus and by the vaccine strain are comparable, which is consistent with the clinical observation that varicella vaccine protects against or significantly reduces the clinical symptoms caused by primary VZV infection. Widespread use of the varicella vaccine in healthy children will yield further knowledge about host-virus interactions, such as the role of exogenous re-exposure in maintaining persistent immunity, which will be relevant to vaccine strategies to prevent other human herpesvirus infections.